TWI837083B - Manufacturing method of lithium ion cathode, lithium ion cathode and battery including the lithium ion cathode - Google Patents

Abstract

An improved method for forming a lithium-ion cathode material specifically for use in a battery. The method includes forming a solution containing a decomposable raw material of a first metal suitable for forming a cathode oxide precursor and a polycarboxylic acid as a first solution. The decomposable raw material is decomposed in the solution to form a first metal salt, wherein the first metal salt serves as a salt for removing protons from the polycarboxylic acid to form a cathode oxide precursor. The cathode oxide precursor is heated to form a lithium-ion cathode material.

Description

Method for manufacturing lithium ion cathode, lithium ion cathode and battery containing the lithium ion cathode

This invention claims priority to U.S. Provisional Patent Application No. 62/447,598 filed on January 18, 2017 and U.S. Provisional Patent Application No. 62/483,777 filed on April 10, 2017, both of which are incorporated herein by reference.

The present invention relates to improved methods for forming fine and ultrafine powders and nanopowders for lithium ion cathodes for batteries. More specifically, the present invention relates to, but is not limited to, lithium ion battery cathodes and methods for efficiently preparing spinel materials and other advanced materials with minimal material waste and reduced process steps such as sintering and calcining that are detrimental to subsequent steps.

There is a need for improvements in batteries. There are two main applications for batteries, one is stationary applications and the other is mobile applications. In both stationary and mobile applications, it is desirable to increase storage capacity, extend battery life, achieve full charge more quickly, and reduce cost. Lithium-ion batteries comprising a lithium metal oxide cathode are very advantageous as suitable batteries in most applications, and they have found support in a variety of applications. However, it is particularly desirable to improve the storage capacity, recharge time, cost and storage stability of lithium-ion batteries. The present invention is primarily directed to lithium-ion batteries in spinel form or rock salt crystal form and improvements in the process for their manufacture.

Preparation of lithium ion batteries in rock salt crystal form comprising a lithium salt and a transition metal based cathode is described in U.S. Patent Nos. 5,511,621, 9,136,534, 9,159,999 and 9,478,807 and U.S. Published Patent Application Nos. 2014/0271413, 2014/0272568 and 2014/0272580, each of which is incorporated herein by reference. The cathode material in rock salt crystal form has the following general formula: LiNi _a Mn _b X _c O ₂

Wherein X is preferably Co or Al, and a+b+c=1. For convenience, when X is cobalt, the cathode material is referred to as NMC, and for convenience, when X is aluminum, the cathode material is referred to as NCA. In the preparation of rock salt crystal form, the transition metal can be precipitated in the form of carbonate by adding a stoichiometric equivalent of lithium carbonate to form a cathode material precursor. The cathode material precursor is then sintered to form the cathode material. The cathode material having a spinel crystal structure has the following general formula: LiNi _x Mn _y Co _z O ₄

where x+y+z=2. In spinel, the lithium stoichiometry is half the transition metal stoichiometry. Therefore, when synthesizing cathode material precursors, the carbonate obtained from lithium carbonate is insufficient to precipitate the transition metal. Excess carbonate addition can only be achieved when sodium carbonate is used, either by introducing unwanted counterions such as sodium, or complicates pH control and may lead to insufficient precipitation, such as when ammonium carbonate is added. In principle, a two-fold stoichiometric excess of lithium carbonate can be used and removed by decanting the aqueous supernatant, however this is undesirable due to the sensitivity of cell performance to changes in lithium stoichiometry.

Improved methods for making lithium-ion cathodes, particularly lithium/manganese/nickel-based cathodes, in spinel and rock salt crystal structures have been desired. The present invention provides such a method.

The object of the present invention is to provide an improved method for preparing a cathode for a lithium ion battery.

An object of the present invention is to provide an improved method of forming a lithium metal cathode oxide precursor, wherein the lithium metal oxide is calcined to form a lithium metal oxide cathode.

A specific object of the present invention is to provide an improved method for forming a lithium ion battery comprising a transition metal cathode in a spinel crystal structure or preferably in a rock salt structure selected from NMC and NCA.

A particular feature of the present invention is the ability to produce lithium-ion metal oxide cathodes that contain gradients of transition metal composition throughout the oxide that are predictable and reproducible, thereby modifying the properties of, for example, the intrinsic properties of the core to, for example, the properties of the shell surrounding the core.

One embodiment of the present invention provides a method for forming a lithium ion cathode material, the lithium ion cathode material comprising a decomposable raw material of a metal salt suitable for forming a cathode oxide precursor and a polycarboxylic acid; decomposing the decomposable raw material to form a metal salt in a solution, wherein the metal salt acts as a salt to remove protons from the polycarboxylic acid to form a cathode oxide precursor; and heating the cathode oxide precursor to form the lithium ion cathode material.

Yet another embodiment is provided in a method of forming a lithium ion cathode material, comprising: reacting lithium carbonate, manganese carbonate, and nickel carbonate with oxalic acid, releasing CO2 _(g) and/or _{H2O (l)} to form a precipitate comprising lithium oxalate, manganese oxalate, and nickel oxalate to form a cathode oxide precursor, and heating the cathode oxide precursor to form the lithium ion cathode material.

[Figure 1] provides SEM micrographs of oxalate spray dried cathode oxide precursor and LiNi _0.5 Mn _1.5 O ₄ material calcined at 900 °C for 15 h when using transition metal acetate (top) and carbonate (bottom) feedstocks.

[Figure 2] provides X-ray diffraction (XRD) patterns of manganese oxalate hydrate precipitated from the reaction of manganese carbonate and oxalic acid in water under different conditions.

[Figure 3] shows the curve of voltage as a function of specific capacity for the spinel material formed by the improved technology of the present invention.

[Figure 4] is an XRD pattern of an embodiment of the present invention.

[Figure 5] is a SEM micrograph of an embodiment of the present invention.

[Figure 6] is an XRD pattern of an embodiment of the present invention.

[Figure 7] is a SEM micrograph of an embodiment of the present invention.

[Figure 8] is a diagram of an embodiment of the present invention.

[Figure 9] is a diagram of an embodiment of the present invention.

[Figure 10] is a diagram of an embodiment of the present invention.

[Figure 11] is a diagram of an embodiment of the present invention.

[Figure 12] is a diagram of an embodiment of the present invention.

[Figure 13] is an XRD pattern of an embodiment of the present invention.

[Figure 14] is a diagram of an embodiment of the present invention.

[Figure 15] is a diagram of an embodiment of the present invention.

[Figure 16] is a diagram of an embodiment of the present invention.

[Figure 17] is an XRD pattern of an embodiment of the present invention.

[Figure 18] is a diagram of an embodiment of the present invention.

[Figure 19] is a diagram of an embodiment of the present invention.

[Figure 20] is a diagram of an embodiment of the present invention.

[Figure 21] is a diagram of an embodiment of the present invention.

[Figure 22] is a diagram of an embodiment of the present invention.

[Figure 23] is a diagram of an embodiment of the present invention.

[Figure 24] is a diagram of an embodiment of the present invention.

[Figure 25] is an XRD pattern of an embodiment of the present invention.

[Figure 26] is an XRD pattern of an embodiment of the present invention.

[Figure 27] is an XRD pattern of an embodiment of the present invention.

[Figure 28] is an XRD pattern of an embodiment of the present invention.

[Figure 29] is a SEM micrograph of an embodiment of the present invention.

[Figure 30] is an XRD pattern of an embodiment of the present invention.

[Figure 31] is an XRD pattern of an embodiment of the present invention.

[Figure 32] is a SEM micrograph of an embodiment of the present invention.

[Figure 33] is a SEM micrograph of an embodiment of the present invention.

[Figure 34] is a diagram of an embodiment of the present invention

[Figure 35] is an XRD pattern of an embodiment of the present invention.

[Figure 36] is an XRD pattern of an embodiment of the present invention.

[Figure 37] is a SEM micrograph of an embodiment of the present invention.

[Figure 38] is a SEM micrograph of an embodiment of the present invention.

[Figure 39] is a diagram of an embodiment of the present invention.

[Figure 40] is a diagram of an embodiment of the present invention.

[Figure 41] is an XRD pattern of an embodiment of the present invention.

[Figure 42] is a diagram of an embodiment of the present invention.

[Figure 43] is a diagram of an embodiment of the present invention.

[Figure 44] is an XRD pattern of an embodiment of the present invention.

[Figure 45] is a SEM micrograph of an embodiment of the present invention.

[Figure 46] is a diagram of an embodiment of the present invention.

[Figure 47] is an XRD pattern of an embodiment of the present invention.

[Figure 48] is a SEM micrograph of an embodiment of the present invention.

[Figure 49] is an XRD pattern of an embodiment of the present invention.

[Figure 50] is a SEM micrograph of an embodiment of the present invention.

[Figure 51] is a diagram of an embodiment of the present invention.

[Figure 52] is a diagram of an embodiment of the present invention.

[Figure 53] is a diagram of an embodiment of the present invention.

The present invention relates to an improved method for preparing a lithium ion battery, in particular a cathode for a lithium ion battery. More specifically, the present invention relates to an improved method for forming a cathode for a lithium ion battery, wherein the cathode is in a spinel form or a rock salt form, preferably a rock salt form of NMC and NCA materials.

0.2；或由化學式II所定義的岩鹽結晶結構；LiNi_aMn_bX_cG_dO₂化學式II其中G是可選的摻雜劑；X是Co或Al；且 其中a+b+c+d=1且d

0.1。 In a preferred embodiment, the lithium metal compound of the present invention comprises a lithium metal compound having a spinel crystal structure defined by Chemical Formula I: LiNi _x Mn _y Co _z E _w O ₄ Chemical Formula I wherein E is an optional dopant; and X+Y+Z+W=2 and w

0.2; or a rock salt crystal structure defined by Formula II; LiNi _a Mn _b X _c G _d O ₂ Formula II wherein G is an optional dopant; X is Co or Al; and wherein a+b+c+d=1 and d

0.1.

x

0.6；1.4

y

1.5且z

0.9。更優選地，0.5

x

0.55，1.45

y

1.5且z

0.05。在一個優選實施例中，x和y都不為零。在化學式I中，優選地Mn/Ni比不大於3，優選地至少2.33至小於3，最優選地至少2.6至小於3。 In the spinel crystal structure of formula I, the preferred embodiment is 0.5

x

0.6; 1.4

y

1.5 and z

0.9. More preferably, 0.5

x

0.55, 1.45

y

1.5 and z

In a preferred embodiment, x and y are both non-zero. In Formula I, the Mn/Ni ratio is preferably not greater than 3, preferably at least 2.33 to less than 3, and most preferably at least 2.6 to less than 3.

a

0.9，更優選地由NMC 622呈現的0.58

a

0.62或如NMC811所呈現的0.78

a

0.82。在優選實施例中，由NMC 111呈現的a=b=c。 In a preferred embodiment of the rock salt crystal structure of Formula II, it is a high nickel NMC, wherein 0.5

a

0.9, preferably 0.58 presented by NMC 622

a

0.62 or 0.78 as shown by NMC811

a

0.82. In a preferred embodiment, a=b=c presented by NMC 111.

In chemical formulas throughout this specification, lithium is defined stoichiometrically to balance charge and with the understanding that lithium is mobile between the anode and cathode. Thus, at any given time, the cathode can be relatively rich in lithium or relatively depleted in lithium. In a lithium-depleted cathode, the lithium will be below stoichiometric equilibrium, and when charging, the lithium can be above stoichiometric equilibrium. Likewise, in formulations listed throughout this specification, metals are expressed as charge balances, with the understanding that since perfectly balanced stoichiometries cannot be formulated in practice, it is possible that the metal may be slightly rich or slightly depleted as determined by elemental analysis.

Dopants may be added to enhance the properties of the oxide, such as electronic conductivity and stability. The dopant is preferably a substitute dopant added with the primary nickel, manganese and optionally cobalt or aluminum. The dopant preferably represents no more than 10 mol %, preferably no more than 5 mol % of the oxide. Preferred dopants include Al, Gd, Ti, Zr, Mg, Ca, Sr, Ba, Cr, Cu, Fe, Zn, V, Bi, Nb and B, with Al and Gd being particularly preferred.

As will be described more fully herein, the cathode is formed from a cathode oxide precursor comprising a salt of Li, Ni, Mn, Co, Al or Fe. The cathode oxide precursor is calcined to form a cathode material that is a lithium metal oxide. The cathode material is optionally treated with a phosphate XPO ₄ , wherein X is an atom required for balancing the charge, and X can be a monovalent atom, a divalent atom or a trivalent atom, and it is understood that it can be combined as required. It is particularly preferred that X can be easily removed by washing or vaporization after application. The phosphate is applied to the surface of the metal oxide, wherein the phosphate portion forms MnPO ₄ on the surface of the metal oxide, or is bonded to the surface of the metal oxide. Manganese is preferably predominantly in the +3 oxidation state, preferably less than 10% of the surface manganese is in the +2 oxidation state, and thereby the manganese is reduced to Mn ²⁺ on the surface. The reaction releases X which is removed by washing or evaporation. In preferred phosphates, X is selected from NH ₄ ⁺ , H ⁺ , Li ⁺ , Na ⁺ and combinations thereof. Particularly preferred phosphates include (NH ₄ ) ₃ PO ₄ , (NH ₄ ) ₂ HPO ₄ , (NH ₄ )H ₂ PO ₄ and H ₃ PO ₄ due to the ease of removing X after forming the surface manganese phosphate. The native manganese oxide of the calcined cathode oxide precursor preferably reacts with the phosphate rather than with added manganese or other metals. Thus, the added phosphate is preferably relatively free of Mn, more preferably less than 1 wt% manganese. Preferably, Mn ⁺² is not added with the phosphate or after the oxide is formed. Preferably, there is no separate manganese phosphate such as a manganese phosphate phase on the surface. Preferably, the phosphate is attached to the surface of the metal oxide.

The cathodic oxide precursor is formed by the reaction of a salt in the presence of a counter ion that forms a relatively insoluble salt. The relatively insoluble salt is believed to form suspended crystals that are believed to be Oswald ripening and eventually precipitate in an ordered lattice. For the purposes of the present invention, preferably salts of manganese and nickel and optionally cobalt or aluminum are combined in a solution containing counter ions that precipitate manganese, nickel and cobalt or aluminum at a rate sufficient to allow crystal growth. Soluble counter ions of manganese, nickel, cobalt or aluminum are those having a solubility of at least 0.1 grams of salt per 100 grams of solvent at 20°C, including acetates, nitrates, carbonates. Metals precipitate as insoluble salts with a solubility of less than 0.05 g of salt per 100 g of solvent at 20°C, including carbonates and oxalates.

The entire reaction involves two sequential secondary reactions, the first of which is the decomposition of the carbonate raw material in the presence of an excess of polycarboxylic acid as shown in Reaction Scheme A:

Wherein X represents a metal suitable for cathode materials, preferably selected from Li ₂ , Mn, Ni, Co or Al. In reaction A, for simplicity, the polycarboxylic acid not shown in reaction A releases acid. The result of reaction A is a metal salt in solution, wherein the salt is chelated by the deprotonated polycarboxylic acid shown in reaction B: X ²⁺ + ^- OOCR ₁ COO ^- →X(OOCR ₁ COO) reaction B

wherein R ¹ represents an alkyl chain comprising a polycarboxylic acid salt. The salt represented by X(OOCR ₁ COO) precipitates in an ordered lattice as described elsewhere herein.

The metal carbonate of reaction formula A may be replaced by a metal acetate such as Li( _{O2CCH3 )} , Ni( _{O2CCH3 ) 2} , or Mn( _O2CCH3 ) ₂ , which may _be added as an aqueous solution or as a solid substance.

If necessary, the pH value (acidity and alkalinity) can be adjusted with ammonium hydroxide due to its simplicity and improved performance for precise control of pH value. In the prior art methods, the use of ammonium hydroxide is difficult because NH ₃ tends to complex with nickel in aqueous solution, and the reaction is as follows:

The result is incomplete precipitation of nickel, which complicates the determination and control of the stoichiometry of the final cathodic oxide precursor. Polycarboxylic acids, especially oxalic acid, are effective in preferentially coordinating nickel with _NH4 ⁺ , thereby increasing the precipitation rate and incorporating nickel into the ordered cathodic oxide precursor. Polycarboxylic acids preferentially precipitate nickel, avoiding the use of ammonium hydroxide.

A particularly preferred embodiment is represented by the formation of LiNi _0.5 Mn _1.5 O ₄ from a cathode oxide precursor represented by the following reaction, preferably aqueous:

Wherein the NiC ₂ O ₄ and MnC ₂ O ₄ are precipitated as a cathode oxide precursor in the form of an ordered lattice, wherein Li ₂ C ₂ O ₄ is precipitated thereon when water is removed. The cathode oxide precursor having a total composition of (Li ₂ C ₂ O ₄ ) _0.5 (NiC ₂ O ₄ ) _0.5 (MnC ₂ O ₄ ) _1.5 is calcined, resulting in the following reaction:

The carbonate decomposition process in the presence of a polycarboxylic acid comprises combining a metal carbonate and oxalic acid in a reactor in the presence of water, followed by stirring. The slurry is then dried, preferably by spray drying, and then calcined. The calcination temperature varies in the range of 400-1000°C to form materials with different structural properties, such as different degrees of Mn/Ni cation ordering in spinel LiNi _0.5 Mn _1.5 O ₄ .

A particular feature of the carbonate decomposition process is that there is no need to grind or mix the cathodic oxide precursor powder, filter the slurry or decant the floating surface, although these steps can be done if desired.

The carbonate decomposition process or decomposition (hydrolysis) _{-precipitation} reaction using oxalate as an example can be described by the following equation, preferably occurring in the presence of water: _{H2C2O4 (aq)} + XCO3 _(s) → CO2 _(g) + _{H2O (l)} + _{XC2O4 (s, aq)} (X = transition metal, _Li2 )

Without being bound by theory, it is assumed that oxalic acid hydrolyzes carbonate to form CO _2(g) , H ₂ O _(l) and metal ions. The transition metal ions are subsequently precipitated as metal oxalate. Depending on the water content, the lithium oxalate may precipitate or remain soluble in the water. It is expected that the soluble lithium oxalate is coated on the transition metal oxalate particles during the spray drying process. It is not necessary for the metal carbonate or oxalic acid to be completely dissolved, because the water is merely a medium for decomposing the metal carbonate and precipitating the metal oxalate in a controlled manner, thereby allowing nucleation and crystal growth. The rate of the decomposition (hydrolysis)-precipitation reaction depends on the temperature, water content, pH, the introduced gas and the crystal structure and morphology of the raw materials.

In a preferred embodiment, due to the increased decomposition reaction rate, the reaction can be completed within a temperature range of 10-100°C at the water reflux temperature.

The water content may vary from about 1 to about 400 ml per 1 g (gram) of oxalic acid, with a lower water content being preferred since the reaction rate is increased and less water must subsequently be removed.

The pH of the solution can be varied from 0 to 12. A particular advantage of the carbonate decomposition process is that the reaction can be carried out without additional pH control, thus simplifying the process and requiring no additional process controls or additives.

Although the reaction can be conducted under untreated atmosphere, other gases may be used in some embodiments, such as CO ₂ , N ₂ , Ar, other inert gases, or O ₂ . In some embodiments, N ₂ and CO ₂ bubbling into the solution are preferred because they can slightly increase the crystallinity of the precipitated metal oxalate.

The crystallinity and morphology of the cathodic oxide precursors, such as amorphous versus crystalline carbonate feedstocks, can affect the decomposition rate due to differences in solubility and particle size and size range.

The carbonate decomposition process proceeds through a series of equilibria from solid carbonate feedstock to solid oxalate precursor species. For the purposes of this discussion, we can divide the process into several different steps according to the following reactions:

(1) H ₂ C ₂ O _4(s) →H ₂ C ₂ O _4(aq) (oxalic acid dissolution)

(2) H ₂ C ₂ O _4(aq) ←→ H ⁺ _(aq) + HC ₂ O ₄ ^- _(aq) (oxalic acid dissociation step 1, _pKa = 1.25)

(3) HC ₂ O ₄ ^- _(aq) ←→ H ⁺ _(aq) + C ₂ O ₄ ^2- _(aq) (oxalic acid dissociation step 2, pK _a =4.19)

(4) XCO _{3(s, aq)} +2H ⁺ _(aq) →X ²⁺ +H ₂ O _(l) +CO _2(g) (carbonate hydrolysis)

(5)X ²⁺ _(aq) +C ₂ O ₄ ^2- _(aq) →XC ₂ O _4(s) (metal oxalate precipitation)

If this reaction is to be used to produce a high voltage _{LiNi0.5Mn1.5O4} material, the following reaction will occur, which will preferably _, but not necessarily _, be carried out in the presence of _H2O :

(6) 0.25Li ₂ CO _3(s) + 0.25NiCO _3(s) + 0.75MnCO _3(s) + 1.25H ₂ C ₂ O _4(aq) → 0.25Li ₂ C ₂ O _4(aq) + Ni _0.25 Mn _0.75 C ₂ O _4(s) + 1.25CO _2(g) + 1.25H ₂ O _(l)

For the purpose of discussion and explanation, the reactions are written step by step with the understanding that the reactions can occur simultaneously under the operating reaction conditions. By varying various reaction parameters such as water content/ionic strength, excess oxalic acid content, batch size, temperature, atmosphere, refluxing reaction mixture, pH control, etc., the rate of each step can be controlled and other desired parameters such as solids content can be optimized.

The carbonate decomposition process can be described as proceeding in a series of equilibria, with both the generation of CO _2(g) from solution as in reaction 4 above and the precipitation of highly insoluble metal oxalates as in reaction 5 above driving the reaction to completion.

The rate of carbonate hydrolysis is related to the K _sp of the metal carbonate and is provided for convenience as follows: lithium carbonate, Li ₂ CO ₃ 8.15×10 ^-4 very fast (seconds to minutes); nickel (II) carbonate, NiCO ₃ , 1.42×10 ^-7 fast (minutes); manganese (II) carbonate, MnCO ₃ , 2.24×10 ^-11 slower (hours to days); and aluminum hydroxide (Al(OH) ₃ , 3x10 ^-34 very slow

The uniformity of the co-precipitation can depend on the rate of carbonate hydrolysis. For example, if _nickel (II) carbonate is completely hydrolyzed before manganese (II) carbonate, it can be precipitated as _NiC2O4 and _{MnC2O4 ,} respectively.

Temperature can be controlled because it affects the rate of oxalic acid dissolution, carbonate hydrolysis, and precipitation of metal oxalates. Specifically, it will be useful to conduct the reaction at the reflux temperature of the water. CO2 _(g) is produced in this reaction, and increasing the temperature will increase the rate of CO2 _(g) removal, so increasing the temperature may increase the carbonate hydrolysis rate due to the lower solubility of CO2(g) at higher temperatures.

Gas sparging can also be an effective method to control the reaction rate by varying the rate of CO ₂ evolution. Sparging with _{N 2(g)} , O _2(g) , CO _2(g) , and/or atmospheric air can be beneficial as the gas can act to displace dissolved CO _2(g) or improve mixing of the reactants.

If the carbonates are first in the form of metastable bicarbonates, they can decompose more quickly. For example, for Li ₂ CO ₃ the following reaction occurs: Li ₂ CO _3(s) +CO _2(g) +H ₂ O _(l) ←→ 2 LiHCO _3(aq)

Metastable lithium bicarbonate is much more soluble than Li ₂ CO ₃ , and the subsequent hydrolysis can proceed stoichiometrically with a single proton as follows: LiHCO _3(aq) +H ⁺ _(aq) →H ₂ O _(l) +CO _2(g) +Li ⁺ _(aq)l

Instead of proceeding as in reaction 4 above.

Divalent metal oxalates such as _{NiC2O4 , MnC2O4} , _CoC2O4 , _{ZnC2O4 ,} etc. are highly insoluble, however monovalent metal _oxalates such as _Li2C2O4 are slightly _soluble with a solubility of ₈ g/100 mL in water at 25°C. If lithium _oxalate must be dissolved in solution and evenly dispersed in the mixed metal oxalate precipitate, it may be necessary to keep the water volume above the solubility limit of lithium oxalate.

The rates of carbonate hydrolysis, metal oxalate precipitation, and the crystal structure and particle size of the metal oxalate precipitate are affected by pH and water content or ionic strength. In some embodiments, it may be beneficial to work at higher ionic strength or lower water content because this increases the proton activity of oxalic acid and the precipitation rate of the metal oxalate. The water content can be normalized to the carbonate feed content, and the preferred ratio of moles of carbonate to the volume of water in L ranges from about 0.05 to about 20. For every 1.25 moles of carbonate water content of about 1.64 L, the ratio of moles of carbonate to the volume of water in L is 1.79, which is suitable for demonstration of the present invention.

Stoichiometric amounts of oxalate and carbonate are sufficient to achieve complete precipitation. However, adding excess oxalic acid can increase the reaction rate because the second proton on oxalic acid is much less acidic and participates in the hydrolysis. Approximately 5% excess oxalic acid on a molar basis to carbonate is sufficient to ensure complete carbonate hydrolysis. ICP analysis showed that a 10% excess of oxalic acid completed the reaction leaving a similar number of Mn/Ni ions in solution as the 0% stoichiometric excess. A small stoichiometric excess of oxalic acid should be effective in achieving complete precipitation, however a low stoichiometric excess may affect the rate of carbonate hydrolysis.

A particular advantage of the carbonate decomposition process is the ability to carry out the entire reaction to completion in a single reactor. Since the lithium source is ideally in solution prior to the spray drying and calcination steps, it may be useful and/or possible to precipitate the transition metal separately and add the lithium source as an aqueous lithium salt solution as the oxalate salt after co-precipitation.

The invention is applicable to transition metal acetate and mixed carbonate feedstocks, thereby making the solubility of the metal compounds more closely matched. Consider a mixed carbonate feedstock such as Ni _0.25 Mn _0.75 CO ₃ + Li ₂ CO ₃ to produce LiNi _0.5 Mn _1.5 O ₄ material. Feedstock impurities can be critical to the properties of the final material. In particular, the MnCO ₃ sample may contain small amounts of unknown impurities that are not hydrolyzed during reflux.

The polycarboxylic acid contains at least two carboxyl groups. A particularly preferred polycarboxylic acid is oxalic acid, in part to minimize the carbon that must be removed during calcination. Other low molecular weight dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, and adipic acid can be used. Higher molecular weight dicarboxylic acids can be used, especially even numbers of carbon with higher solubility, however the necessity to remove the extra carbon and reduce solubility makes them less desirable. Other acids such as citric acid, oxalylacetic acid, fumaric acid, maleic acid, and other polycarboxylic acids can be used provided they have sufficient solubility to achieve at least a small stoichiometric excess and have sufficient chelating properties. Acids with hydroxyl groups cannot be used due to their increased hygroscopicity.

To complete the reaction to form the cathode oxide precursor, a solution of the starting salt is prepared. Preferably, an additive solution is prepared, which preferably contains nickel, manganese and cobalt or aluminum solutions, said solutions generally, individually or in some combination, and preferably a bulk solution containing lithium. The additive solution is then added to the bulk solution as described elsewhere herein. The solution can be reversed, however, it is preferred to add the transition metal in a predetermined stoichiometry, and thus it is advantageous to add it as a single solution containing all the transition metals to the bulk solution containing lithium.

Each solution is prepared by dissolving the solid in a chosen solvent, preferably a polar solvent such as water, but not limited thereto. The choice of solvent depends on the solubility of the solid reactant in the solvent and the dissolution temperature. Dissolution at ambient temperature and at a rapid rate so that dissolution is not energy intensive is preferred. Dissolution may be performed at slightly higher temperatures, but preferably below 100°C. Other dissolution aids may be the addition of acids or bases.

During mixing, a gas is preferably bubbled into the bulk solution. For purposes of discussion, a gas is defined as inert, which does not contribute to the chemical reaction, or a gas is defined as reactive, which adjusts the pH or promotes the chemical reaction. Preferred gases include air, CO ₂ , NH ₃ , SF ₆ , HF, HCl, N ₂ , helium, argon, methane, ethane, propane, or mixtures thereof. Unless the reactant solution is sensitive to air, particularly preferred gases include ambient air. If it is necessary to reduce the atmospheric environment, carbon dioxide is particularly preferred and it can also be used as a solvent, as a pH regulator or if carbonates are formed as reactants. Ammonia can also be introduced as a gas to adjust the pH. Ammonia can form ammonia compounds with transition metals and can help dissolve such solids. As an example, a gas mixture such as 10% O ₂ in argon may be used.

To form the cathodic oxide precursor, the pH is preferably at least about 1 to no more than about 9.6, without limitation. Ammonia or ammonium hydroxide is suitable for increasing the pH, as is any soluble base, which is particularly preferred since LiOH is required. Acids, particularly formic acid, are suitable for lowering the pH if necessary. In one embodiment, lithium may be added, for example by adding lithium acetate to achieve a sufficient solids content, typically about 20 to 30 wt %, prior to drying.

A particular advantage of the present invention is the ability to create a transition metal concentration gradient throughout the oxide body, where a region, such as the center, can have a transition metal ratio and this ratio can progress through the oxide body in a continuous or stepwise manner.

Considering that NMC is provided for purposes of discussion and clarification without limitation, the concentrations of Ni, Mn, and Co may vary radially from the core to the surface of the particle. In the exemplary embodiments provided for clarity, the Ni content may be in a gradient, thereby allowing for a relatively low Ni concentration at or near the surface of the oxide particle and a relatively high Ni concentration in the core of the oxide particle. Based on neutral stoichiometry, the ratio of Li to transition metal will remain constant throughout the oxide particle. For example, the overall composition of Ni:Mn:Co may be 6:2:2 and 8:1:1 for NMC 622 and NMC 811, respectively, with the core being relatively rich in one transition metal and the shell being relatively poor in the same transition metal. More specifically, the core can be enriched in one transition metal, such as nickel, with the ratio of transition metal to transition metal decreasing radially. For example, a NMC8:1:1 core can have an NMC6:2:2 shell on the outside with an NMC1:1:1 shell on the outside as a non-limiting example. These reactions can be done in stepwise additions or in a continuous gradient by varying the pumping rate of the transition metal. The ratio of transition metal in each addition and the number of additions can be varied to obtain the desired gradient distribution.

A particular feature of the present invention is the ability to preferentially incorporate dopants and other materials into the oxide interior or towards or even at the surface. With prior art, dopants are for example uniformly dispersed within the oxide. Furthermore, any surface treatment such as aluminum is on the formed oxide as a surface reactant and not necessarily as atoms bonded into the oxide lattice. The present invention allows dopants to be systematically dispersed at the core, as would be the case if the dopant was incorporated into the initial transition metal slurry, in radial bands if the dopant was incorporated into a subsequent transition metal slurry or shell, as would be the case if the dopant was incorporated into the final transition metal slurry.

For purposes of the present invention, each radial portion of an oxide particle will be defined based on the percentage of transition metal used to form that portion. For example, if the initial slurry has a first proportion of transition metal, and the initial slurry contains 10 mole % of the total transition metal used to form the oxide, the core will be considered to be 10% oxide by volume, and the composition of the core will be defined as having the same proportion as the first proportion of transition metal. Similarly, each shell surrounding the core will be defined by the percentage of transition metal therein. As a non-limiting example, a cathode oxide precursor formed using three slurries, each with equal moles of transition metal, wherein the first slurry has a Ni:Mn:Co ratio of 8:1:1, the second slurry has a Ni:Mn:Co ratio of 6:2:2, and the third slurry has a Ni:Mn:Co ratio of 1:1:1 would be considered to form an oxide representing 1/3 of the volume of the oxide particles having a core to transition metal ratio of 8:1:1, a first shell on the core representing 1/3 of the volume of the oxide particles having a transition metal ratio of 6:2:2, and a periphery on the first shell representing 1/3 of the volume of the oxide particles having a transition metal ratio of 1:1:1, without regard to transition metal migration that may occur during sintering of the cathode oxide precursor.

In particularly preferred embodiments, the dopant is incorporated into a shell of a specific dopant having aluminum. More preferably, the shell containing the dopant represents less than 10% of the volume of the oxide particles, even more preferably less than 5% of the volume of the oxide particles, and most preferably no more than 1% of the volume of the oxide particles. For the purposes of the present invention, a dopant is defined as a material that is precipitated with at least one transition metal selected from Ni, Mn, Co, Al and Fe during the formation of the cathode oxide precursor. More preferably, the cathode oxide precursor comprises Ni and Mn and optionally Co or Al. Materials added after the completion of the deposition of at least one transition metal are defined herein as surface treatments.

After the reaction to form the cathode oxide precursor is completed, the resulting slurry mixture is dried to remove the solvent and obtain a dry cathode oxide precursor powder. Any type of drying method and equipment can be used, including a spray dryer, a tray dryer, a freeze dryer, etc. selected according to the final product. The drying temperature will be defined and limited by the equipment used, and such drying is preferably below 350°C, more preferably 200-325°C. An evaporator can be used for drying so that the slurry mixture is placed in a tray and the solvent is released as the temperature rises. Any industrially used evaporator can be used. A particularly preferred drying method is a spray dryer with a fluidized nozzle or a rotary atomizer. These nozzles are preferably of a diameter that is the smallest size appropriate to the size of the cathodic oxide precursor in the slurry mixture. Due to cost considerations, the drying medium is preferably air.

The particle size of the cathode oxide precursor is nano-sized primary and secondary particles, up to small-sized secondary particles of aggregates as small as 50 microns, which are easily crushed to smaller sizes. It should be known that the composition of the final powder also affects the morphology. The cathode oxide precursor has a preferred particle size of about 1-5 μm . If a spray dryer, freeze dryer, etc. is used, the resulting mixture is continuously stirred while being pumped into the spray dryer head. For a disk dryer, the liquid evaporates from the surface of the solution.

The dried powder is transferred to the calcining system in batches or by conveyor. In large-scale production, this transfer may be continuous or batch. The calcining system may be a box furnace using ceramic trays or saggers as containers, a rotary calciner, a fluidized bed that may be co-current or counter-current, a rotary tube furnace and other similar equipment, but is not limited to these.

The heating rate and cooling rate during calcination depend on the type of end product desired. Generally, a heating rate of about 5°C per minute is preferred, but common industrial heating rates are also applicable.

The final powder obtained after the calcination step is a fine, ultrafine or nano-sized powder that may not require additional crushing, grinding or milling as currently performed in conventional processing. The particles are relatively soft and do not sinter as in conventional processing.

The final calcined oxide powder is preferably surface characterized, tested for particle size by electron microscopy, porosity, elemental chemical analysis and preferably the properties required for the specific application. The spray dried cathodic oxide precursor is preferably of very fine nano-size.

The spray dryer collector can be modified so that the outlet valve can be opened and closed as the spray powder is transferred to the calciner. In batches, the spray dried powder in the collector can be transferred to a tray or sack and moved into the calciner. A rotary calciner or a fluidized bed calciner can be used to demonstrate the invention. The calcination temperature is determined by the composition of the powder and the desired final phase purity. For most oxide type powders, the calcination temperature ranges from as low as 400°C to slightly above 1000°C. After calcination, the powders are sieved because they are soft and not sintered. The calcined oxides do not require long grinding times and do not require grading to obtain a narrow particle size distribution.

_{LiM2O4 spinel} oxide has a preferred crystallite size of 1-5 μm . _LiMO2 rock salt oxide has a preferred crystallite size of about 50-250 nm, more preferably about 150-200 nm.

A particular advantage of the present invention is the formation of metal chelates of polycarboxylic acids rather than acetates. Acetates act as a combustion fuel during the subsequent calcination of the cathodic oxide precursor and require additional oxygen for adequate combustion. Lower molecular weight polycarboxylic acids, particularly lower molecular weight dicarboxylic acids, and more particularly oxalic acid, decompose at lower temperatures without the introduction of additional oxygen. For example, oxalates decompose at about 300°C and do not require additional oxygen, allowing for more accurate control of the calcination temperature. This can allow for reduced firing temperatures, thereby promoting the formation of a disordered Fd-3m spinel crystal structure with minimal impurity phases as seen at higher temperatures.

This method for forming a cathode oxide precursor is referred to herein as a compound precursor formulation (CPF) method, which is suitable for large-scale industrial production of high-performance fine, ultrafine and nanoscale powders that require defined unique chemical and physical properties to meet performance specifications for specialized applications. The CPF method provides a cathode oxide precursor in which the metal is precipitated in the form of a salt into an ordered lattice. The cathode oxide precursor is then calcined to form an oxide. Although not limited to theory, it is assumed that the formation of an ordered lattice facilitates the formation of the oxide during calcination, as opposed to an amorphous solid.

The CPF process provides the controlled formation of specialized microstructures or nanostructures, and a final product having particle size, surface area, porosity, phase purity, chemical purity and other essential properties suitable for meeting performance specifications. Powders produced by the CPF process are obtained with reduced processing steps relative to currently used technologies and can utilize currently available industrial equipment.

The CPF method is applicable to any inorganic powder and organometallic powder with electrophilic or nucleophilic ligands. The CPF method can use low-cost raw materials as starting materials, and additional purification or separation can be performed in situ if necessary. The inert or oxidizing atmospheric conditions required for powder synthesis can be easily achieved using the equipment of this method. The reaction temperature can be ambient temperature or slightly warm, but preferably not more than 100°C.

The CPF method produces fine, ultrafine and nanoscale powders of cathode oxide precursors in a simple and effective manner by integrating the chemical principles of crystallization, solubility, transition complex formation, phase chemistry, acidity and alkalinity, aqueous chemistry, thermodynamics and surface chemistry.

The time when crystallization begins, especially when the nucleation step begins, is the most critical stage in the formation of nanoscale powders. A particular advantage offered by CPF is the ability to prepare nanosized particles at the beginning of this nucleation step. The solute molecules from the starting reactants are dispersed in a given solvent and are in solution. In this case, clusters are believed to begin to form at the nanoscale under the right conditions of temperature, supersaturation and other conditions. These clusters constitute nuclei in which atoms begin to arrange in a defined and periodic manner, which subsequently defines the crystalline microstructure. Crystal size and shape are macroscopic properties of the crystal resulting from the internal lattice structure.

After nucleation begins, crystal growth also begins, and both can occur simultaneously as long as supersaturation exists. The rates of nucleation and growth are determined by the existing supersaturation in the solution, and depending on the supersaturation state, nucleation or growth occurs over the other. It is very critical to determine the concentrations of the required reactants in order to tune the crystal size and shape. If nucleation dominates growth, finer crystal sizes will be obtained. The nucleation step is a very critical step, and the reaction conditions in this initial step define the crystals obtained. By definition, nucleation is the initial phase transition of a small area, such as the formation of crystals from a liquid solution. This is the result of local, violent fluctuations on a molecular scale in a homogeneous phase that is in a metastable equilibrium state. Total nucleation is the combined effect of two types of nucleation - primary and secondary. In primary nucleation, crystals form without any crystals to start with. Secondary nucleation occurs when crystals form to initiate the nucleation process. It is this consideration and the importance of the primary nucleation step that forms the basis of the CPF method.

In the CPF process, the reactants are preferably dissolved in solution at ambient temperature or, if necessary, at slightly higher temperatures but preferably not exceeding 100°C. The selection of inexpensive starting materials and suitable solvents are important aspects of the present invention. The purity of the starting materials is also important as this affects the purity of the final product, which may require a specific purity level required by its performance specifications. Therefore, low-cost starting materials that can be purified during the preparation process without significantly increasing the processing costs must be considered.

CPF uses conventional equipment to intimately mix the reactants, preferably including a highly agitated mixture, preferably with gas sparging, particularly when a reactive gas is advantageous.

The gas is preferably introduced directly into the solution, without limitation to the method of introduction. The gas can be introduced into the solution within the reactor by having multiple gas diffusers (e.g., tubes) located on the side of the reactor, wherein the tubes have holes for the gas to be discharged. Another configuration is to have a double-walled reactor so that the gas passes through the inner wall of the reactor. There can also be a gas inlet at the bottom of the reactor. The gas can also be introduced through a stirrer shaft, producing bubbles upon exiting. Several other configurations are possible, and the description of these arrangements given here is not limited to these.

In one embodiment, the aerator can be used as a gas diffuser. The gas diffusion aerator can be incorporated into the reactor. Ceramic diffusion aerators are tubular or dome-shaped and are particularly suitable for demonstration of the present invention. The pore structure of the ceramic foam diffuser can produce relatively fine small bubbles, resulting in a very high gas-liquid interface per cubic foot per minute (cfm) of gas provided. Due to the slow rate of fine bubbles, the high gas-liquid interface ratio combined with the increase in contact time can provide a higher transfer rate. The porosity of the ceramic is a key factor in the formation of bubbles and contributes significantly to the nucleation process. Although not limited to this for most configurations, a gas flow rate of at least one liter of gas per minute per liter of solution per minute is suitable for demonstration of the present invention.

Ceramic tube gas diffusers on the side of the reactor wall are particularly suitable for demonstration of the present invention. Several of these tubes can be placed at different locations, preferably equidistant from each other, to more evenly distribute the gas throughout the reactor. The gas is preferably introduced into the diffuser within the reactor through a fitting connected to a header assembly, which slightly pressurizes the chamber of the tube. As the gas permeates through the ceramic diffuser body, tiny bubbles may begin to form due to the porous structure of the material and the surface tension of the liquid outside the ceramic tube. Once the surface tension is overcome, a tiny bubble is formed. This small bubble then rises through the liquid, forming an interface for transfer between gas and liquid before reaching the liquid surface.

The dome-shaped diffuser can be placed at the bottom of the reactor or on the side of the reactor. For the dome-shaped diffuser, a bubble flow is usually generated that continuously rises from the bottom to the surface to provide a large reaction surface.

A membrane diffuser that closes when the air flow is insufficient to overcome surface tension is suitable for use in demonstrations of the present invention. This is useful to prevent any product powder from entering the diffuser.

In order to have higher gas efficiency and utilization, it is preferred to reduce gas flow and pressure and consume less pumping energy. The diffuser can be configured so that for the same volume of gas, smaller bubbles with a higher surface area are formed, rather than fewer larger bubbles. A larger surface area means that the gas dissolves faster in the liquid. This is advantageous in solutions where the gas is also used to dissolve reactants by increasing its solubility in the solution.

A nozzle, preferably a one-way nozzle, can be used to introduce gas into the solution reactor. The gas can be delivered using a pump, and the flow rate should be controlled to achieve the desired bubbles and bubble rate. A nozzle diffuser, preferably on at least one side or bottom of the reactor, is suitable for demonstration of the present invention.

The rate at which the gas is introduced is preferably sufficient to increase the volume of the solution by at least 5%, in addition to the action of the agitator. In most cases, at least about one liter of gas per minute per liter of solution is sufficient to demonstrate the invention. It is preferred to recycle the gas back to the reactor.

To transfer the added solution to the bulk solution, it is best to use a tube connected to a pump for the solution to be transferred to the reactor. The tube entering the reactor is preferably a tube with a single hole or multiple holes with a selected predetermined inner diameter so that the diameter size can deliver the stream of added solution at a given rate. An atomizer with a fine nozzle is suitable for delivering the added solution to the reactor. The end of the transfer tube can include a nozzle to provide multiple added solution streams simultaneously. In large-scale production, the transfer rate is a time factor, so the transfer rate should be fast enough to produce the required appropriate size.

The agitator may be equipped with a plurality of propellers of different configurations, each propeller comprising one or more propellers which are angled relative to one another or in the same plane. Furthermore, the mixer may have one or more sets of these propellers. The goal is to produce sufficient agitation in the liquid. Straight propellers or angled propellers are suitable. The size and design of these propellers determine the type of flow of the solution and the direction of the flow. Speeds of at least about 100 revolutions per minute (rpm's) are suitable for the present invention.

The transfer rate of the added solution has a kinetic effect on the nucleation rate from the bulk solution. The preferred approach is to have fine transfer flows to control the local concentrations of reactants that affect nucleation and the relationship of the nucleation growth rate to the crystal growth rate. For smaller sized powders, slower transfer rates will produce finer powders. The correct conditions for competitive nucleation and growth must be determined by the final powder characteristics. The temperature of the reaction is preferably ambient or mild temperatures, if desired.

The specific nanostructure is formed in advance and transferred to the final product, thereby improving the performance of the material in the desired application. For the purpose of this invention, a nanostructure is defined as a structure of primary particles with an average size of 100 to 300 nm.

Neither surfactants nor emulsifiers are required. In fact, it is preferred that surfactants and emulsifiers are not used as they may inhibit drying.

Size control can be achieved by concentration of the solution, gas flow rate or transfer rate of added solution into the bulk solution.

No repeated and cumbersome grinding and sorting steps are required.

Reduced calcination times can be achieved and repeated calcinations are usually not necessary.

The reaction temperature is the ambient temperature. If dissolution is required, the temperature should not exceed 100°C.

Customized physical properties of powders such as surface area, porosity, tap density, and particle size can be carefully controlled by selecting reaction conditions and starting materials.

The process is amenable to large-scale manufacturing using currently available equipment and/or innovations in industrial equipment.

Implementation example

Preparation of electrodes

The composite electrode was prepared by mixing the active material with 10 wt% conductive additive as a conductive additive and 5 wt% polyvinylidene fluoride (PVDF) as a binder, and then dissolved in N-methyl-2-pyrrolidone (NMP) solvent. The slurry was cast on graphite-coated aluminum foil and vacuum dried at 60°C overnight. Electrode disks with an area of 1.54 ^cm2 were cut from the electrode sheet, with a typical loading of 4 mg.cm ^-2 .

Button battery assembly

The button cells were assembled in an argon-filled glove box. Lithium foil (340 μm ) was used as the counter electrode and reference electrode in the half-cell, and a commercially available Li ₄ Ti ₅ O ₁₂ (LTO) composite electrode was used as the counter electrode and reference electrode in the full cell. 1M LiPF ₆ in 7:3 (vol%) ethylene carbonate (EC): diethylene carbonate (DEC) was used as the electrolyte. The electrodes were separated by one or two 25 μm thick Celgard ^® membranes (half-cell) and one Celgard membrane full cell.

Loop Protocol

The spinel cathode cells were charged at various C-rates (1C rate equals 146mAg ^-1 ) at 25°C over a voltage range of 3.5V-4.9V using an Arbin Instrument battery tester (Model BT2000). At the end of the 1C or higher rate constant current charging step, a 4.9V, 10-minute constant voltage charging step was applied to the cells. The rock salt NMC cells were charged at various C-rates (1C rate equals 200mAg ^-1 ) at 25°C over a voltage range of 2.7V-4.35V. At the end of the constant current charging step at 1C or higher rate, a constant voltage charging step of 4.35V is applied to the battery for 10 minutes.

Example 1: SEM analysis of the spray-dried mixed oxalate precursor and calcined material from the production of LiNi _0.5 Mn _1.5 O ₄ cathode material were both crystalline and provided similar material morphologies as shown in FIG. 1 using transition metal acetate and carbonate feedstocks.

Example 2: Figure 2 shows the XRD patterns of manganese oxalate hydrate precipitated by the reaction of manganese carbonate and oxalic acid (5 excess mol%) in water for 6 hours (a) at room temperature in air (b) at room temperature with nitrogen bubbling (c) at room temperature with carbon dioxide bubbling (d) at water reflux temperature in air (e) at room temperature at 10 times the water content of the previous experiments (ad). The XRD pattern of the material precipitated in the experiment (ac) matches the XRD pattern of manganese oxalate dihydrate with the space group C2 / c . Bubbling nitrogen and _carbon dioxide gases has a slight effect on the crystallinity of the material. _The reaction at water reflux temperature (b) produces two different phases _of manganese oxalate dihydrate; one in the C2 / c space group and one in the P212121 space group. When the concentration of the reactants was reduced to 1/10 of that in experiment (ad), a one-dimensional chain-like structure of the inter-polymer [[heavy naphtha (II)]-oxalate] monohydrate] space group Pcca was formed. These experiments show that reaction conditions such as temperature, concentration and atmosphere have a significant effect on the precipitation products of manganese carbonate and oxalic acid in water.

Example 3: A particular problem with LiNi _0.5 MN _1.5 O ₄ spinel is a phenomenon known as the 4V plateau, in which the voltage drops from 4.7 V to 4.0 V at the end of the discharge, as shown in FIG3 . The plateau is believed to be the result of the formation of Mn ³⁺ due to oxygen loss during sintering in air. In the results of the prior art process shown in FIG3 , an ordered cathode oxide precursor is formed as a precipitate comprising nickel carbonate and manganese carbonate, and the cathode oxide precursor is calcined using a stoichiometric amount of lithium acetate to provide the spinel LiNi _0.43 Mn _1.57 O ₄ in which the Mn:Ni ratio is 3.70. The charge capacity is measured as a function of voltage, resulting in the significant 4 volt plateau shown in FIG3 .

In Invention A, oxalate is formed from transition metal acetate, resulting in a significant reduction in the 4 volt plateau, as shown in Figure 3. In Invention A, lithium carbonate, nickel acetate and manganese acetate are decomposed with oxalic acid in the process shown in Figure 3 to form an ordered precursor to an oxide. The cathode oxide precursor is then calcined to obtain spinel LiNi _0.48 Mn _1.52 O ₄ , where the Mn:Ni ratio is 3.13. The discharge capacity is measured as a function of voltage, as shown in Figure 3, with a significant reduction in the 4 volt plateau.

In invention B, metal carbonate is used as a raw material, and the carbonate is decomposed with oxalate, resulting in the substantial elimination of the 4 volt plateau, especially the use of a slightly excess of nickel, wherein the ratio of Mn to Ni is no longer preferably at least 2.33 to less than 3, and most preferably 2.64 to less than 3. The ordered cathode oxide precursor is formed by lithium carbonate, nickel carbonate and manganese carbonate decomposed with oxalic acid in the method mentioned in Figure 3 as an optimized process. The cathode oxide precursor is calcined to obtain spinel LiNi _0.51 Mn _1.49 O ₄ , wherein the Mn: Ni ratio is 2.90. The discharge capacity is measured as a function of voltage, and the 4 volt platform is almost completely eliminated, as shown in Figure 3.

Example 4: Synthesis of a cathode oxide precursor of a high pressure spinel having the formula LiNi _0.5 Mn _1.5 O ₄ using lithium carbonate, nickel carbonate, manganese carbonate and oxalic acid. 820.0 g of H ₂ C ₂ O ₄ .2H ₂ O was added to 2.0 L of water in a chemical reactor vessel at a temperature of about 40° C. In a second vessel, a carbonate mixture slurry containing Li ₂ CO ₃ (96.1 g), NiCO ₃ (148.4 g), MnCO ₃ (431.1 g) in 1.2 L of deionized water was prepared. The carbonate mixture slurry was pumped into the chemical reactor vessel at a rate of about 0.2-0.3 L/h. The mixture in the reactor was vigorously mixed at 40° C. under atmospheric environment to form a slurry. The slurry was dried using a spray dryer to produce a high pressure spinel cathode oxide precursor material. An X-ray diffraction (XRD) pattern is provided in Figure 4 and a scanning electron microscope (SEM) image of the dried powder is provided in Figure 5. The XRD diffraction indicates a highly ordered lattice and the SEM shows a nanostructured crystalline material.

Example 5: A high-pressure spinel having the chemical formula LiNi _0.5 Mn _1.5 O ₄ was prepared from the cathode oxide precursor of Example 4. The cathode oxide precursor of Example 4 was placed in an alumina pot and calcined in a box furnace in an atmospheric environment at 900° C. for 15 hours. The resulting powder was analyzed by powder X-ray diffraction analysis to obtain the diffraction pattern provided in FIG6 . The SEM provided in FIG7 shows that the nanostructure of the cathode oxide precursor remains essentially unchanged. The lattice parameter of the spinel structure was calculated to be 8.174 (1) Å. The electrochemical properties of the synthesized material were evaluated as a cathode in a half-cell relative to a lithium metal anode and as a cathode in a full cell relative to a Li ₄ Ti ₅ O ₁₂ (LTO) anode. The discharge capacity of the battery as a function of the half-cell at 0.1C is shown in Figure 8. The specific capacity at 1C rate at 25°C in the half-cell as a function of the cycle is shown in Figure 9. The specific capacity at different discharge rates at 25oC in the half-cell is shown in Figure 10. The specific capacity at 1C at 25°C in the full cell with LTO anode is shown in Figure 11.

Example 6: A high-pressure spinel having the chemical formula LiNi _0.5 Mn _1.5 O ₄ was prepared from the cathode oxide precursor of Example 4. The cathode oxide precursor material was placed in an alumina boat and fired in a tubular furnace at an oxygen flow rate of 50 cm ³ /min. The firing steps as shown in Figure 12 included a pre-firing step at 350°C, firing at 900°C and slow cooling to 650°C annealing. In addition to slow cooling, combustion in oxygen alleviates oxygen deficiency and leads to a reduction in the 4V platform usually observed in these materials. The X-ray diffraction of the obtained powder is shown in Figure 13, and based on this, the lattice parameter of the spinel structure is calculated to be 8.168 (1) A. The electrochemical performance of the synthesized materials was evaluated as cathodes in half cells relative to a lithium metal anode. The voltage curves obtained at a discharge rate of 0.1C at 25°C in the half cell are shown in Figure 14. A particular feature is the absence of the 4V voltage plateau typically observed in these materials. The specific capacities obtained at a 1C cycle rate at 25°C in the half cell are shown in Figure 15. The specific capacities obtained at different discharge rates at 25°C in the half cell are shown in Figure 16.

Example 7: The cathode oxide precursor material of Example 4 was placed in an alumina pot and fired in a box furnace in an atmospheric environment using the firing procedure shown in Figure 12. The X-ray diffraction pattern of the resulting powder is shown in Figure 17, and the lattice parameter of the spinel structure is calculated to be 8.169(1)Å. The electrochemical performance of the synthesized material was evaluated as a cathode in a half-cell relative to a lithium metal anode. In the half-cell, the discharge rate was 0.1C and the voltage at a discharge rate of 25°C is shown in Figure 18. The specific capacity obtained by the half-cell at a discharge rate of 1C at 25°C is shown in Figure 19.

Example 8: 8.62 g of MnCO ₃ (Alfa; particle size: 1-3 μm ), 2.97 g of NiCO ₃ (Alfa; anhydrous) and 1.92 g of high pressure spinel having the chemical formula LiNi _0.5 Mn _1.5 O ₄ were used as starting materials with lithium carbonate. 16.4 g of oxalic acid dihydrate (H ₂ C ₂ O ₄ .2H ₂ O) was used as a chelating agent. The metal carbonate was mixed with 20 mL of deionized water to form a slurry in a beaker, and the acid was added to 40 mL of deionized water in another beaker. The oxalic acid slurry was then heated to 40° C. and the carbonate slurry was added to the acid solution at a rate of 8.9 mL/hour to form a cathode oxide precursor. The cathode oxide precursor was dried in a spray dryer. The dried cathode oxide precursor was baked in an alumina pan at 900°C in an atmospheric atmosphere for 15 hours. Figure 20 shows the voltage measured as a function of the discharge rate of 0.1C at 25°C in a half cell.

74μm)之外，與實施例8類似地合成具有化學式LiNi_0.5Mn_1.5O₄的高壓尖晶石的陰極氧化物前驅物。與實施例8相似，將陰極氧化物前驅物乾燥並焙燒。在圖21中示出了在半電池中在25℃下以0.1C的放電速率測量的作為放電的函數的電壓。 Example 9: In addition to using MnCO ₃ with a larger particle size (Sigma; particle size:

A cathode oxide precursor of a high pressure spinel having the formula LiNi _0.5 Mn _1.5 O ₄ was synthesized similarly to Example 8, except that the cathode oxide precursor had a 74 μm diameter. The cathode oxide precursor was dried and calcined similarly to Example 8. The voltage as a function of discharge measured at a discharge rate of 0.1 C at 25° C. in a half cell is shown in FIG. 21 .

7μm)，2.97g的NiCO₃(Alfa；無水)和1.92g的碳酸鋰作為合成高壓尖晶石LiNi_0.5Mn_1.5O₄的前驅物起始材料。使用16.4g草酸二水合物(H₂C₂O₄.2H₂O)作為螯合劑。將金屬碳酸鹽與80mL去離子水混合以在一個燒杯中形成漿液，並將酸溶解在單獨燒杯內的120mL去離子水中。在約25℃的環境溫度下，以16mL/hr的速度將碳酸鹽漿料加入到草酸溶液中以形成陰極氧化物前驅物。然後使用噴霧乾燥器乾燥陰極氧化物前驅物。將乾燥的陰極氧化物前驅物在900℃的氧化鋁鍋中在大氣環境中焙燒15小時。在圖22中示出了在半個電池中在25℃以0.1C的放電率測量的作為放電的函數的電壓。 Example 10: 8.62 g of MnCO ₃ (Sigma; particle size:

7μm), 2.97g of _NiCO3 (Alfa; anhydrous) and _1.92g of lithium carbonate _were used as precursor starting materials for _the synthesis of high-pressure spinel _{LiNi0.5Mn1.5O4} . 16.4g of oxalic acid dihydrate ( _H2C2O4.2H2O ) was used as a chelating agent. The metal carbonate _was mixed with 80mL of deionized water to form a slurry in a beaker _, and the acid was dissolved in 120mL of deionized water in a separate beaker. At an ambient temperature of about 25°C, the carbonate slurry was added to the oxalic acid solution at a rate of 16mL/hr to form a cathode oxide precursor. The cathode oxide precursor was then dried using a spray dryer. The dried cathode oxide precursor was baked in an alumina pan at 900°C in an atmospheric environment for 15 hours. The voltage as a function of discharge measured at 25°C and a discharge rate of 0.1C in a half cell is shown in FIG.

Example 11: A cathodic oxide precursor of a high pressure spinel having the chemical formula LiNi _0.5 Mn _1.5 O ₄ was synthesized similarly to Example 10, except that less water was used in the reaction: the same amount of metal carbonate was added to 28 mL of water with 12 mL of deionized water and the same amount of oxalic acid. The carbonate slurry was added to the oxalic acid slurry at a rate of 3 mL/hr. The cathodic oxide precursor was then dried and fired similarly to Example 7. The voltage as a function of discharge measured at a discharge rate of 0.1 C at 25° C. in a half cell is shown in FIG. 23. Example 11 illustrates the use of very small amounts of added water, and in some examples, no water is added because the water provided by decomposition and the water of hydration of the starting materials may be sufficient to initiate and complete the reaction.

Example 12: A cathode oxide precursor of a high pressure spinel having the formula LiNi _0.5 Mn _1.5 O ₄ was synthesized similarly to Example 11, except that alkaline nickel carbonate (Sigma; NiCO ₃ .2Ni(OH) ₂ .xH ₂ O) was used. The cathode oxide precursor was then dried and fired similarly to Example 11. The voltage as a function of discharge measured at 25° C. at a discharge rate of 0.1 C in a half cell is shown in FIG. 24 .

74μm)，2.97g的NiCO₃(Alfa；無水)和1.92g的鋰(LiCl)，合成具有化學式LiNi_0.5Mn_1.5O₄的高壓尖晶石的前驅物碳酸鹽作為原料。使用16.4g草酸二水合物(H₂C₂O₄.2H₂O)作為螯合劑。將金屬碳酸鹽與80mL去離子水混合以在一個燒杯中形成漿液，並將酸溶解在單獨燒杯內的160mL去離子水中。然後將含有溶解的草酸的燒杯置於冰浴中保持約5℃的溫度。將碳酸鹽漿液以23mL/hr的速度添加到草酸溶液中。圖25中提供了乾燥陰極氧化物前驅物的XRD圖。 Example 13: 8.62 g of MnCO ₃ (Sigma; particle size:

74μm), 2.97g of NiCO ₃ (Alfa; anhydrous) and 1.92g of lithium (LiCl) were used as raw materials to synthesize a high-pressure spinel precursor with the chemical formula LiNi _0.5 Mn _1.5 O _4. 16.4g of oxalic acid dihydrate (H ₂ C ₂ O ₄ .2H ₂ O) was used as a chelating agent. The metal carbonate was mixed with 80mL of deionized water to form a slurry in a beaker, and the acid was dissolved in 160mL of deionized water in a separate beaker. The beaker containing the dissolved oxalic acid was then placed in an ice bath to maintain a temperature of about 5°C. The carbonate slurry was added to the oxalic acid solution at a rate of 23mL/hr. The XRD pattern of the dry cathode oxide precursor is provided in Figure 25.

Example 14: A cathode oxide precursor having a high pressure spinel of the precursor having the chemical formula LiNi _0.5 Mn _1.5 O ₄ was synthesized similarly to Example 13, except that the synthesis was performed at the boiling point of water (100° C.). A reflux condenser was used to maintain the water level of the reaction. The XRD pattern of the dried cathode oxide precursor is provided in FIG. 26 .

Example 15: A cathode oxide precursor of spinel having the chemical formula LiMn ₂ O ₄ was synthesized using lithium carbonate, manganese carbonate and oxalic acid as raw materials. 16.39 grams of H ₂ C ₂ O ₄ .2H ₂ O was added to 40 milliliters of water in a beaker. In a second beaker, Li ₂ CO ₃ (1.85 g) and MnCO ₃ (11.49 g) were mixed in 24 ml of deionized water. The carbonate mixture slurry was pumped into the oxalic acid slurry at a rate of 0.01 L/Hr. The mixture in the reactor was mixed at ambient temperature. The obtained slurry was dried by evaporation to produce a cathode oxide precursor of LiMn ₂ O _4. The XRD spectrum is shown in Figure 27.

The cathode oxide precursor material was calcined in a box furnace in air at 350°C for 1 hour and then at 850°C for 5 hours. The X-ray diffraction pattern and scanning electron microscopy pattern of the calcined material are shown in Figures 28 and 29, respectively.

Example 16: A cathode oxide precursor of spinel of the chemical formula LiMn ₂ M _0.1 O ₄ (M: Mn, Al, Ni) was synthesized using metal carbonate and oxalic acid in the amounts shown in Table 1.

The raw materials of each composition were mixed in 32 _ml of deionized water at ambient temperature for 6 hours. The resulting slurry was dried by evaporation. The X-ray diffraction pattern shown in Figure 30 shows that manganese oxalate dihydrate (sample A), cathode oxide precursor of LiMn ₂ O ₄ and cathode oxide precursor of LiMn _1.9 Al _0.1 O _{4 (} sample _B ) crystallized in the orthorhombic space group (P 2 1 2 1 2 1). LiMn _1.9 Ni _0.1 O ₄ (sample C) crystallized in the monoclinic space group (C2/c).

Example 17: A cathode oxide precursor of NMC 111 with the chemical formula LiNi _0.333 Mn _0.333 Co _0.333 O 2 was prepared from 3.88 g Li ₂ CO ₃ , 3.79 g NiCO ₃ , 3.92 g MnCO ₃ , 3.93 g CoCO ₃ and 19.23 g H ₂ C ₂ O ₄ ．2H ₂ O dispersed in 240 mL deionized water. The mixture was heated to reflux _for 6.5 hours and cooled. The solid content of the final mixture was about 13%. A powder was obtained by spray drying to obtain a cathode oxide precursor with the chemical formula LiNi _0.333 Mn _0.333 Co _0.333 (C ₂ O ₄ ) _1.5 . The cathode oxide precursor was heated at 110°C for 1 hour and then calcined in a box furnace at 800°C for 7.5 hours in air to obtain NMC 111. The SEM image of the cathode oxide precursor is shown in FIG32. The XRD pattern of the calcined powder is shown in FIG31, and the SEM of the calcined powder is shown in FIG33, in which the nanostructure of the cathode oxide precursor is shown to remain substantially unchanged. The relationship between the discharge capacity and the number of cycles is shown in FIG34.

Example 18: A cathode oxide precursor of NMC 622 having the chemical formula LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was prepared from 39 g Li ₂ CO ₃ , 71 g NiCO ₃ , 23 g MnCO ₃ and 24 g CoCO ₃ dispersed in 200 mL deionized water in a beaker. The carbonate mixture was pumped into a separate beaker containing 201 g H ₂ C ₂ O ₄ 2H ₂ O in 400 mL deionized water at a rate of 0.38 mol carbonate per hour. The reaction mixture was then stirred for 1 hour. The final mixture having a solid content of about 20% was spray dried to obtain a cathode oxide precursor of the chemical formula LiNi _0.6 Mn _0.2 Co _0.2 (C ₂ O ₄ ) _1.5 . The XRD pattern of the cathode oxide precursor is provided in FIG. 35 and the SEM is provided in FIG. 37 . The cathode oxide precursor was heated at 110° C. for 1 hour and then calcined at 800° C. in air for 7.5 hours in a box furnace to obtain NMC 622, which has the XRD pattern shown in FIG. 36 and the SEM of FIG. 38 . SEM demonstrates that the ordered nanostructure lattice of the cathode oxide precursor is substantially maintained in the calcined powder. The discharge capacity of half a battery is 1C at 1C, and the functional relationship with the number of cycles is shown in FIG. 39 . Figure 40 shows the initial charge and discharge voltage curves as a function of capacity at 0.1C.

Example 19: A cathode oxide precursor of NMC 811 having the chemical formula LiNi _0.8 Mn _0.1 Co _0.1 O ₂ was prepared from 39 g Li ₂ CO ₃ , 95 g NiCO ₃ , 12 g MnCO ₃ and 12 g CoCO ₃ dispersed in 200 mL deionized water in a beaker. The mixture was pumped into a separate beaker containing 201 g H ₂ C ₂ O ₄ .2H ₂ O in 400 mL deionized water at a rate of 0.38 mol carbonate per hour. The reaction mixture was then stirred for 1 hour. The final mixture with a solid content of about 20% was spray dried to obtain a cathode oxide precursor of the chemical formula LiNi _0.8 Mn _0.1 Co _0.1 (C ₂ O ₄ ) _1.5 . The precursor was heated in air in a box furnace at 600° C. for 5 hours, heated at 125° C. for 1 hour under an oxygen flow, and calcined in a tubular furnace at 830° C. for 15 hours under an oxygen flow to obtain NMC 811. FIG41 provides an XRD pattern of NMC 811 oxide. The discharge capacity as a function of the cycle is shown in FIG42, and the voltage curve as a function of the capacity is shown in FIG43. NMC 811 was heated at 125°C for 1 hour and then calcined at 830°C for 15 hours in a tubular furnace under an oxygen flow to form pre-calcined NMC 811. The XRD pattern of the pre-calcined XRD is shown in Figure 44 and the SEM is shown in Figure 2. The discharge capacity is provided in Figure 46, where the solid line represents the average capacity and the error line represents the maximum and minimum capacity of a series of samples.

Example 20: An NCA precursor of the chemical formula LiNi _0.8 Mn _0.15 Al _0.05 O ₂ was prepared from 8 g Li ₂ CO ₃ , 19 g NiCO ₃ , 2 g Al(OH)(CH ₃ COO) ₂ and 4 g CoCO ₃ dispersed in 40 mL deionized water in a beaker. The mixture was pumped into a separate beaker containing 40 g H ₂ C ₂ O ₄ 2H ₂ O in 80 g deionized water at a rate of 0.08 mol carbonate per hour. The reaction mixture was then stirred for 1 hour. The final mixture having a solid content of about 20% was spray dried to obtain a cathode oxide precursor of the chemical formula LiNi _0.8 Mn _0.15 Al _0.0.05 (C ₂ O ₄ ) _1.5 . The cathode oxide precursor was heated at 125° C. for 1 hour and then calcined at 830° C. for 15 hours in a tubular furnace under an oxygen flow to obtain NCA. An XRD pattern is provided in FIG. 47 and an SEM is provided in FIG. 48 , in which the layered nanostructure derived from the cathode oxide precursor is easily observed.

Example 21: NMC 622 having an overall chemical formula of LiNi _0.6 Mn _0.2 Co _0.2 O ₂ was prepared with a stepwise concentration gradient of the transition metal from the central portion or core to the outer portion. The cathode oxide precursor was prepared by dispersing 3.9 g of Li ₂ CO ₃ , 9.5 g of NiCO ₃ , 1.2 g of MnCO ₃ and 1.2 g of CoCO ₃ containing the first metal as a salt in 10 mL of deionized water from a beaker. The mixture was pumped into a separate beaker containing 40.4 g of H ₂ C ₂ O ₄ .2H ₂ O in 80 mL of deionized water to form a cathode oxide precursor containing a core of the first metal salt. Subsequently, a mixture comprising 1.0 g Li ₂ CO ₃ , 1.8 g NiCO ₃ , 0.6 g MnCO ₃ and 0.6 g CoCO ₃ dispersed in 5 mL of deionized water containing a second metal as a salt was pumped into the reaction mixture to form a first shell of a cathode oxide precursor containing a second metal salt around the core. Another mixture comprising 2.9 g Li ₂ CO ₃ , 3.0 g NiCO ₃ , 2.9 g MnCO ₃ and 3.0 g CoCO ₃ was dispersed in 10 mL of deionized water and pumped into the reaction mixture to form a third ratio in a second shell around the first shell. The addition rate of each solution was kept constant at 15 mL/hour. The reaction mixture was then stirred for 1 hour and spray dried to obtain a cathode oxide precursor having an overall chemical formula of LiNi _0.6 Mn _0.2 Co _0.2 (C ₂ O ₄ ) _1.5 . The cathode oxide precursor is then heated at 110°C for 1 hour and then calcined in a box furnace in air at 800°C for 7.5 hours to obtain a gradient NMC622 with a nickel-rich core NMC811 of the chemical formula LiNi _0.8 Mn _0.1 Co _0.1 O ₂ , a first shell of NMC622 representing the volume of LiNi _0.6 Mn _0.2 Co _0.2 O ₂ and an outer NMC111 shell of the chemical formula LiNi _0.333 Mn _0.333 Co _0.333 O ₂ form. The invention thus allows the surface characteristics to be different from the volume. The XRD pattern of the stepwise NMC is provided in Figure 49 and the SEM is provided in Figure 50. The discharge capacity as a function of the cycle is provided in Figure 51. NMC 622 (Example 15 is provided in Figure 52), NMC 811 (Example 16), double-burned NMC 811 (Example 16), NCA (Example 17) and NMC gradient (Example 18), and their normalized graphs are shown in Figure 53.

The present invention has been described above with reference to the preferred embodiments of the present invention, but is not limited thereto. A person skilled in the art will recognize additional embodiments and improvements within the scope of the present invention that are not specifically described herein but are more specifically described in the appended claims.

Claims (56)

A method for manufacturing a lithium ion cathode comprises: forming a solution as a first solution comprising a solvent, a decomposable raw material of a soluble salt of a first metal suitable for forming a cathode oxide precursor, and a polycarboxylic acid, wherein the first solution comprises soluble counter ions of manganese, nickel, cobalt or aluminum, and the soluble counter ions have a relative humidity of 100 g of the solvent at 20°C. at least 0.1 gram of salt solubility; decomposing the decomposable raw material to form a first metal salt, wherein the first metal salt precipitates as an ordered lattice as a salt for removing protons from the polycarboxylic acid to form the cathode oxide precursor; drying the cathode oxide precursor with a spray dryer; and heating the cathode oxide precursor to form the lithium ion cathode. According to the method for manufacturing a lithium ion cathode of item 1 of the patent application, the decomposable raw material is a carbonate, hydroxide or acetate of the first metal, wherein the first metal is selected from the group consisting of Li, Mn, Ni, Co, Al and Fe. According to the method for manufacturing a lithium ion cathode of item 2 of the patent application, the decomposable raw material includes at least one of lithium carbonate, manganese carbonate and nickel carbonate. According to the method for manufacturing a lithium ion cathode in item 3 of the patent application, the decomposable raw materials include lithium carbonate, manganese carbonate and nickel carbonate. According to the method for manufacturing a lithium ion cathode of item 3 of the patent application, the decomposable raw material also contains at least one of cobalt carbonate or aluminum hydroxide. According to the method for manufacturing a lithium ion cathode of claim 1, the polycarboxylic acid is selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, citric acid, oxalylacetic acid, fumaric acid and maleic acid. According to the method for manufacturing a lithium ion cathode of claim 6, the polycarboxylic acid is oxalic acid. According to the method for manufacturing a lithium ion cathode of claim 1, the lithium ion cathode is defined by chemical formula I: LiNi _x Mn _y Co _z E _e O ₄ Chemical formula I wherein E is a dopant x+y+z+e=2; and 0

e

0.2. According to the method for manufacturing a lithium ion cathode of claim 8, the chemical formula I is in the form of spinel crystals. According to the method for manufacturing a lithium ion cathode of claim 8, wherein both x and y are not zero. According to the method for manufacturing a lithium ion cathode of claim 10, the lithium ion cathode is LiNi _0.5 Mn _1.5 O ₄ . According to the method for manufacturing a lithium ion cathode of claim 8, the lithium ion cathode is defined by LiNi _x Mn _y O ₄ , wherein 0.5

x

0.6 and 1.4

y

1.5. According to the method for manufacturing a lithium ion cathode of claim 12, wherein 0.5

x

0.55 and 1.45

y

1.5. A method for manufacturing a lithium ion cathode according to claim 8, wherein the lithium ion cathode has a molar ratio of Mn to Ni of no more than 3. A method for manufacturing a lithium ion cathode according to claim 14, wherein the lithium ion cathode has a molar ratio of Mn to Ni of at least 2.33 to less than 3. A method for manufacturing a lithium ion cathode according to claim 15, wherein the lithium ion cathode has a molar ratio of Mn to Ni of at least 2.64 to less than 3. According to the method for manufacturing a lithium ion cathode of item 8 of the patent application, the dopant is selected from the group consisting of Al, Gd, Ti, Zr, Mg, Ca, Sr, Ba, Cr, Fe, Cu, Zn, V, Bi, Nb and B. According to the method for manufacturing a lithium ion cathode of claim 17, the dopant is selected from the group consisting of Al and Gd. According to the method for manufacturing a lithium ion cathode of claim 1, the lithium ion cathode is defined by chemical formula II: LiNi _a Mn _b X _c G _d O ₂ chemical formula II wherein G is a dopant; X is Co or Al; wherein a+b+c+d=1; and 0

d

0.1. According to the method for manufacturing a lithium ion cathode of claim 19, wherein 0.5

a

0.9. According to the method for manufacturing a lithium ion cathode of claim 20, wherein 0.58

a

0.62 or 0.78

a

0.82. According to the method for manufacturing a lithium ion cathode of item 19 of the patent application, a=b=c. According to the method for manufacturing a lithium ion cathode of claim 1, the heating is performed in air. According to the method for manufacturing a lithium ion cathode of claim 1, the cathode oxide precursor forms a core. According to the manufacturing method of the lithium ion cathode of claim 24, before the heating: adding a second metal suitable for forming another cathode oxide precursor and a second polycarboxylic acid to the decomposable raw material; and decomposing the decomposable raw material to form a second metal salt, wherein the second metal salt is precipitated on the core as a shell. According to the method for manufacturing a lithium ion cathode of item 25 of the patent application, the second metal accounts for no more than 10 mol% of the total molar amount of the first metal and the second metal. According to the method for manufacturing a lithium ion cathode of claim 26, the second metal accounts for no more than 5 mol% of the total molar amount. According to the method for manufacturing a lithium ion cathode of claim 27, the second metal accounts for no more than 1 mol% of the total molar amount. A method for manufacturing a lithium ion cathode according to item 25 of the patent application, wherein the second metal is selected from Ni, Mn, Co, Al, Gd, Ti, Zr, Mg, Ca, Sr, Ba, Cr, Fe, Cu, Zn, V, Bi, Nb and B. According to the method for manufacturing a lithium ion cathode of claim 25, the decomposable raw material contains Al. A method for manufacturing a lithium ion cathode according to claim 25, wherein the core comprises Ni and Mn in a first molar ratio, and the shell comprises Ni and Mn in a second molar ratio. A method for manufacturing a lithium ion cathode according to claim 31, wherein the first molar ratio and the second molar ratio are different. According to the method for manufacturing a lithium ion cathode of claim 32, wherein the first molar ratio has a higher molar ratio of Ni to Mn than the second molar ratio. A method for manufacturing a lithium ion cathode comprises: forming a solution comprising a solvent and a soluble counter ion comprising manganese, nickel, cobalt or aluminum, wherein the soluble counter ion has a solubility of at least 0.1 gram of salt per 100 grams of solvent at 20°C, wherein the soluble counter ion is selected from lithium carbonate, manganese carbonate and nickel carbonate; reacting the lithium carbonate, the manganese carbonate and the nickel carbonate with oxalic acid to release CO2 _(g) and _{H2O (l)} forming a cathode oxide precursor by precipitating an ordered lattice containing lithium oxalate, manganese oxalate and nickel oxalate; drying the cathode oxide precursor with a spray dryer; and heating the cathode oxide precursor to form the lithium ion cathode. According to the method for manufacturing a lithium ion cathode of claim 34, the manganese carbonate and the nickel carbonate are in a first molar ratio and the cathode oxide precursor forms a core. According to the method for manufacturing a lithium ion cathode of claim 35, the method further comprises: before the heating, forming a second slurry containing lithium carbonate, manganese carbonate and nickel carbonate at a second molar ratio; and precipitating a shell of the lithium oxalate, the manganese oxalate and the nickel oxalate on the core, wherein the manganese oxalate and the nickel oxalate of the shell are at the second molar ratio. According to the method for manufacturing a lithium ion cathode of claim 35, the precipitate also contains a dopant. A method for manufacturing a lithium ion cathode according to item 37 of the patent application, wherein the dopant is selected from Al, Gd, Ti, Zr, Mg, Ca, Sr, Ba, Cr, Fe, Zn, Cu, V, Bi, Nb and B. According to the method for manufacturing a lithium ion cathode of claim 38, the dopant is Al. According to the method for manufacturing a lithium ion cathode in item 36 of the patent application, the manganese oxalate and nickel oxalate in the shell account for less than 10 mol% of the total amount of all manganese oxalate and nickel oxalate in the cathode oxide precursor. According to the method for manufacturing a lithium ion cathode of claim 34, the lithium ion cathode is defined by chemical formula I: LiNi _x Mn _y Co _z E _e O ₄ Chemical formula I wherein E is a dopant; x+y+z+e=2; and 0

e

0.1. According to the method for manufacturing a lithium ion cathode of claim 41, the chemical formula I is in the form of spinel crystals. According to the method for manufacturing a lithium ion cathode of claim 41, wherein both x and y are not zero. According to the method for manufacturing a lithium ion cathode of claim 41, the lithium ion cathode is LiNi _0.5 Mn _1.5 O ₄ . According to the method for manufacturing a lithium ion cathode of claim 41, the lithium ion cathode is defined by the formula LiNi _x Mn _y O ₄ , wherein 0.5

x

0.6 and 1.4

y

1.5. According to the method for manufacturing a lithium ion cathode of claim 45, wherein the 0.5

x

0.55 and 1.45

y

1.5. A method for manufacturing a lithium ion cathode according to claim 41, wherein the lithium ion cathode has a molar ratio of Mn to Ni of no more than 3. A method for manufacturing a lithium ion cathode according to claim 47, wherein the lithium ion cathode has a molar ratio of Mn to Ni of at least 2.33 to less than 3. A method for manufacturing a lithium ion cathode according to claim 48, wherein the lithium ion cathode has a molar ratio of Mn to Ni of at least 2.64 to less than 3. A method for manufacturing a lithium ion cathode according to item 41 of the patent application, wherein the dopant is selected from Al, Gd, Ti, Zr, Mg, Ca, Sr, Ba, Cr, Fe, Zn, Cu, V, Bi, Nb and B. According to the method for manufacturing a lithium ion cathode of item 50 of the patent application, the dopant is selected from a group consisting of Al and Gd. According to the method for manufacturing a lithium ion cathode of claim 34, the lithium ion cathode is defined by chemical formula II: LiNi _a Mn _b X _c G _d O ₂ chemical formula II wherein G is a dopant, X is Co or Al, a+b+c+d=1; and

d

0.1. According to the method for manufacturing a lithium ion cathode of claim 52, wherein 0.5

a

0.9. According to the method for manufacturing a lithium ion cathode of claim 53, wherein 0.58

a

0.62 or 0.78

a

0.82. According to the method for manufacturing a lithium ion cathode of item 52 of the patent application, a=b=c. According to the method for manufacturing a lithium ion cathode of claim 34, the heating is carried out in air, oxygen or a mixture thereof.